Method and device for joining sections of thermoplastic continuous web material

ABSTRACT

The invention relates to a method for joining a number of sections ( 7 ) of a thermoplastic continuous web material in order to form an expandable section block ( 2 ). Said block is built up by repeatedly carrying out sequences of steps of the method. The invention also relates to a device for forming said blocks at high speeds.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of U.S. application Ser. No. 10/193,661, filedJul. 11, 2002, now U.S. Pat. No. 6,907,912, which is a continuation ofInternational Application No. PCT/DE00/00070, filed Jan. 11, 2000,designating the U.S. and published under PCT Article 21(2) in German,both of which are incorporated herein in their entirety by reference.

BACKGROUND OF THE INVENTION

This invention concerns a procedure for joining cut pieces of athermoplastic roll material.

SUMMARY OF THE INVENTION

This invention concerns a procedure for joining cut pieces of athermoplastic roll material. The material in particular, is of a fleecetype, consisting of thermoplastic synthetic fibers. The intention is toso bond a multiplicity of the cut strips (“cuts”) of fibrousthermoplastic fleece and/or roll material, that the cured block ofbonded strips may be mechanically expanded. The invention also includesa device for joining cut pieces of a thermoplastic roll material.

The purpose of the invention is to devise a procedure to create a lowdensity block material out of thermally bonded, fibrous, thermoplasticroll and/or sheet material, which can easily become a component in theconstruction of objects, where its properties are of particular use.This procedure is intended to create a block material, which can bemanufactured without the use of chemical adhesives or glue and withoutpre-folding of the roll material, and which may be expanded once joinedtogether. Furthermore, a device shall be created, which can manufacturesuch expandable block materials, which permits a high rate ofproduction. Further advantages of this invention are evident from theperusal of the following description.

The purpose of the aforementioned procedure is attained with thisinvention by the following:

a) positioning each first cut piece parallel with the last cut piece,and all those in between, within each newly created block of cut pieces;

b) the first strips, which are lying opposite one another in the block,shall be heated to the material's welding temperature on the surfaces ofthe first and last cuts;

c) the surfaces of the first and last cuts of each block are joined insuch a way, that the first strips of both cuts meet, at which point thelast cut piece is pressed onto the first piece, whereby the two arewelded or thermally fused;

d) a second cut is brought in a parallel position to the first cut,whereby the flat sides oppose each other;

e) on the surfaces of the first and second cuts, opposing second strips,which are set apart by approximately double the strip width, against thefirst strips, are heated to the material's welding temperature;

f) the second cut and the first cut are joined, such that the stripsmeet, whereby a weld, or thermal fusion occurs, when the first strip ispressed into the second strip; and

g) the steps (a) through (f) are continuously repeated with many furthercuts.

Through this procedure, expandable hobe-material is created without theuse of adhesives or pre-folding of the roll material. This procedure issuitable for reaching high production speeds. Cutting of single strips,of rolls of the material, a separate procedure, which are later joinedby the aforementioned method, precedes this joining procedure. However,it is possible to produce directly from pre-cut pieces, if they aredelivered as such. The product of the procedure, which is the subjectmatter hereof, is the hobe-material, which is delivered as is toend-users, for further work, as this provides for an optimum use offreight space. Of course, it is also possible to expand thehobe-material directly behind the production device, as part of theoverall process. Through the invented procedure, the hobe-material blockis created via cyclical addition of cuts, whereby its cross section isdetermined by the choice of the cut width. The width of the material(which corresponds to the roll width of the original thermoplastic rollmaterial) can be up to 5.2 m or more. The height of the produced blockmaterial corresponds to the width of the roll cuts, which can be freelychosen by the operator.

In accordance with the preferred execution form of the inventedprocedure, the cut, which is to be added, and the produced block ofcuts, which is facing the new cut, which is to be added, are movedtowards one another in steps (c) and (f). This way, an extendedcompression time is available for welding strips together, which haspositive effects on the weld quality.

In accordance with the preferred execution form of the inventedprocedure, the added cut, and the produced block of cuts, are moved insteps (c) and (f), during and/or after the point of contact, by thethickness of one cut parallel to the production direction.Simultaneously with the addition of a new cut, the produced block is,therefore, moved by the thickness of said cut, towards the productiondirection.

Preferably, the newly produced block of cuts is held or wedged undersome pressure exerted vertically against the production direction. Thiswedging or pressure is applied across the front area of the block rank,where the block is produced. This pressure is adjustable and thusenables the adjustment of the pressure used for and during compressionand welding of each new cut or the pressure with which each new cut isjoined with the preceding block.

Appropriately, in order to create newly expanded honeycomb material, oneheats the block, which was created via steps (a) through (g) to atemperature which enables plastic deformation and then expandsvertically from its constituent cuts, i.e. towards the productiondirection.

Surprisingly, it has been shown that the hobe-material block can beexpanded under heating conditions, shortly after its creation, withoutthe risk of separation or even stressing of the newly formed welds. Inthis case, the heat required for the plastic deformation, which is usedfor expansion purposes, is lower than the heat required for weldingpurposes. For example, in the case of roll material made ofpolypropylene fibers, heating between 75 to 85° C. is sufficient forexpansion, whereas the welding temperature lies above 120° C., up to165° C.

Preferably, heating of the produced block occurs via infrared light. Theadvantage of infrared light heating is that the heat remains within theblocking rank, where a partial expansion has already taken place. Theradiant heat (or another form of heating) is directed into the spacesopened up as a result of the partial expansion in order that a fairlyeven heating of the entire block cross section will result.

Preferably one transports the cuts on a circular path, cyclically, intothe welding position in front of the block of joined cuts. This way,many cuts can be transported, one after the other, on a rotor, whichthus enables high rates of production speed.

The purpose is further reached via a device, which joins a multiplicityof cuts of a thermoplastic roll material to form an expandable block ofsuch cut strips. According to this invention, the device will contain anopen-ended magazine, to accept the newly formed block of cuts as well asa rotor, which is positioned in front of this magazine, complete withseveral stations, which are distributed evenly about the circumferenceof the rotor. Each such station contains:

a) a mechanism for carrying the cut strips, which can reach beyond thewidth of the cut;

b) a strip heating mechanism, which is oriented towards the stripcarrying mechanism, which can be driven back and forth between aposition in front of the strip carrying mechanism and a position that ispulled back from the strip carrying mechanism;

c) a pressure mechanism, which is oriented towards the strip carryingmechanism. Preferably, the pressure mechanism is arranged in the rotorturning direction, behind the strip carrying mechanism.

The rotor is located between the open-ended magazine and a transferstation. At the stationary transfer station, the rotor takes on eachnewly cut strip (“cut”) and transports it towards the transfer magazine,which already contains the block, which has been produced thus far. Thewelding, or heat fusion, between the newly cut and correctly positionedstrip and the previously produced block, occurs in this position, infront of the magazine. The stations, which are distributed about thecircumference of the rotor have several functions. They take on andtransport each newly cut strip to the welding position in front of themagazine. They heat up the opposing surfaces of the last strip, which ison the previously produced block, as well as the newly cut, transportedand weld-positioned strip and effect the pressure, through which theweld between these two strips occurs, by squeezing one into the other,while adequately heated.

According to the preferred execution form of the invented device, therotor is equipped with an even number of stations and the strip heatingmechanisms are axially offset from one station to the next. This way,each of the cuts, or strips, which are constituents of the producedblocks, are provided with offset welded strips, as required. At theconclusion of this process, the produced hobe-block can then be expandedto reveal a honeycomb material whereby each honeycomb cell has sixequidistant sides. The even number of stations on the rotor can befreely chosen as the size of the rotor will permit; e.g. six or eightstations are a practical number. The offset of the strip heatingmechanisms of neighboring stations equals twice the width of the weldingstrip in the production of honeycomb material. The pressure mechanismscan extend across the entire width of the strip carrying mechanism.However, it is only across the width of the welding strip, that thepressure mechanisms can exert their pressure. In this case, the pressuremechanisms as well as the strip heating mechanisms are offset fromstation to station.

According to the preferred execution form, the pneumatically drivenstrip carrying mechanisms are provided with drilled holes, which can beconnected to a negative pressure source. At the transfer station, eachcut or strip will be transferred onto the strip carrying mechanism bysuction and thus held in place. In the welding position, in front of themagazine, once heating of each strip, via the strip heating mechanisms,has occurred, the negative pressure is disengaged, so that each strip isavailable for immediate welding, whereby the pressure mechanism thenpresses the correctly prepared strip into the last strip of existingblock, which has thus grown by a further attached strip.

Appropriately, the strip heating mechanisms consist of a number ofchamber-like heating elements, which are offset from station to stationby twice the width of the welding strip. The strip heating mechanisms onthe rotor can be substituted with other strip heating elements ofanother width and an appropriately (and differently) sized distance ofthe chamber-like heating elements. In this way, one may adjust thehoneycomb cell size.

Preferably, the pressure mechanisms are roller-shaped. The rollers canbe equipped with an adjustable spring loading mechanism so that thepressure exerted along the welding strips, in concert with the wedgingof the produced block in the magazine, can be adjusted as required.

When the task at hand is to turn hobe-material into expanded honeycombmaterial, the magazine has to be equipped with a heater and at least onepair of expansion rollers. The heater can consist of a single sided or adouble sided set of infrared lamps. Appropriately, the heat will bedirected towards the welding strips, after the partial expansion andtowards the consequently created channels. The expansion rollers are infact brush rollers, or rollers that have been provided with an elasticmaterial, such that the block, which is intended to be expanded, suffersno damage during the expansion process.

BRIEF DESCRIPTION OF THE DRAWINGS

One execution form of the invented device will be further detailed inthe attached drawing. The following are shown:

FIG. 1 shows an overall view of the device in schematic form;

FIG. 2 shows a frontal view of the chamber-like strip heating mechanism,in an enlarged scale; and

FIG. 3 illustrates the produced block rank in the expansion phase.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENT OF THE INVENTION

FIG. 1 shows a table 1 for the guidance of the newly producedhobe-material block 2, as per this invention. At the front end of thetable 1, there is an open-ended magazine 3 with a securing mechanism(not shown) through which the block 2 can be positioned, subject to anadjustable pressure, vertically towards the production direction. Thetable 1 with the open-ended magazine 3 can be moved or positioned backand forth in the directions indicated by the arrows 4 via a mechanism,which is not shown in this drawing. An infrared radiator 5 is positionedtowards the production direction, behind the open-ended magazine 3,above the hobe block 2, through which the hobe block 2 can be heated toits plastic deformation temperature. In the production direction behindthe table 1 there is a pair of expansion-rollers 15, which grab theblock 2 from the magazine 3 and thus cause the expansion to take place,turning block material into honeycomb material. For the executionversion shown in the drawings, the expansion-rollers 15 were equippedwith brushes. The distance between the upper roller and the lower roller15 is adjustable, in concert with the height of the block 2 and thedesired pressure. Towards the production direction, behind theexpansion-rollers 15, there is a conveyor belt 16, which is intended toaccept and transport the expanded block.

Between the open-ended magazine 3 and the cut magazine 7, there is arotor 6, held in bearings to permit circular motion, which extends alongthe entire cut width. The rotor is connected to a cyclical drivemechanism, which is not shown in the drawing. It is equipped with sixstations spaced equally along its circumference, each of whichtransports one cut or strip, provides it with a welding strip andpresses it into the hobe block 2, in front of the magazine 3. Everystation essentially encompasses three units, specifically a radiallyadjustable and bar-shaped strip carrying mechanism 8, a tangentiallyadjustable strip heating mechanism, situated in front of the stripcarrying mechanism 8, and a roller shaped pressure mechanism 10. Thesethree units essentially extend across the entire width (vertical to theplan view) of the rotor 6. Motion of the strip carrying mechanism 8 andthe comb-shaped strip heating mechanism 9 are guided and drivenpneumatically and centrally through a mechanism which is not shown onthe drawing. The pressure mechanism 10 generally consists of a springloaded roller, which, in concert with the turning motion of the roller,presses the cut, which has been provided with welding strips, from thetop, downwards towards the hobe block 2 and thereby completes thewelding process through which the newly cut and positioned strip isattached to the hobe block 2.

The mode of operation of this device is as follows: In front of the cutmagazine 7, the strip carrying mechanism 8 is activated, while the stripheating mechanism 12 is pulled back, whereby a cut or strip is taken onby the carrying mechanism 8, from the cut magazine 7. During the turningmotion of the rotor 6, in the direction of the arrows 11, the stripheating mechanism 12 is already driven forward so that the cut which hasjust been taken over is positioned between the strip carrying mechanism8 and comb-shaped strip heating mechanism 12. During this process, thestrip carrying mechanism 8 remains in a position, which is drivenbackwards away from the strip heating mechanism 12. As soon as thisstation has completed three cycles and has assumed a position in frontof the open-ended magazine 3, the strip carrying mechanism 8 with thecut or strip, on the table 1, on the one hand, is moved so close to theopen-ended magazine 3 and the hobe material block 2, on the other hand,that they can be contacted by the comb-shaped strip heating mechanism12. Now the comb-shaped strip heating mechanism 12 is pulled backbetween the cut on the strip carrying mechanism 8 and the hobe materialblock 2, whereby the welding strips are formed through contact betweenthe opposing surfaces of the cuts and the hobe material block 2.Finally, the strip carrying mechanism 8 with the cut and the open-endedmagazine 3 with the hobe material block 2 are moved more closely towardone another, until the welding strips come in contact with one another.Following this last step, the strip carrying mechanism 8 and theopen-ended magazine 3 once again separated and the rotor 6 cyclesforward. During this process, the roller of the pressure mechanism 10 ofthis station rolls over the welded cut, whereby a new pressure andforward or pushing motion of the hobe material block 2 is created, whichyields a distance equivalent to the thickness of the cut or strip. Thesepartial processes repeat themselves as soon as the next station of therotor 6 has moved into position in front of the hobe material block 2.

FIG. 2 shows a frontal view of the strip heating mechanism whosechamber-like heating elements 12 are heated electrically to the requiredtemperature in order to effect the welding bonds between strips or cutsof the thermoplastic material.

FIG. 3 shows the hobe material block 2 during a three part transitionfrom the non-expanded hobe block material in area a, through thepartially expanded status in area b, to a substantially expanded statusin area c. The heating via the infrared radiator 5 occurs at leastpartially in area b, so that the radiant heat can reach the inside ofthe block 2.

1. An apparatus for joining multiple pieces of thermoplastic material toform a cellular block, comprising: a supplying mechanism for positioninga new piece to be added to the cellular block in opposing face-to-facerelation with a last piece most recently previously welded to thecellular block; and a welding mechanism for contemporaneously formingmultiple spaced apart and elongate welds between the new piece and thelast piece while the new piece and the last piece are in the opposingface-to-face relation, so that each of the welds extends in alongitudinal direction and the welds are spaced apart from one anotherin a lateral direction, the welding mechanism comprising a pressingdevice and a heating device having a plurality of heating fingers thatextend in the longitudinal direction and are spaced apart in the lateraldirection, the heating device being movable in the longitudinaldirection between an extended position in which the heating fingers arepositioned between the last piece on the block and the new piece to bejoined to the block and are in contact with the opposing surfaces of thenew piece and the last piece to heat the new piece and the last piece atlocations contacted by the heating fingers, and a retracted position inwhich the heating fingers are withdrawn from between the new piece andthe last piece, the pressing device being structured and arranged topress the pieces together after the heating device is moved to theretracted position such that the new piece is welded to the last pieceat said locations.
 2. The apparatus of claim 1, wherein the supplyingmechanism comprises a rotor that is rotatable about an axis parallel tothe lateral direction, and a plurality of carrying mechanisms supportedon the rotor and circumferentially spaced apart along an outer peripheryof the rotor, each carrying mechanism being operable to receive a newpiece to be added to the block and to carry the new piece as the rotoris rotated until the new piece is positioned in alignment with the blocklocated adjacent the rotor, and then to urge the new piece toward theblock.
 3. The apparatus of claim 2, wherein the welding mechanismcomprises a plurality of said heating devices, there being one heatingdevice for each carrying mechanism, the heating devices being supportedon the rotor, each heating device being operable to move into theextended position as the rotor advances the respective carryingmechanism into alignment with the block, and to move into the retractedposition as the respective carrying mechanism is advanced past theblock.
 4. The apparatus of claim 3, wherein the welding mechanismcomprises a plurality of said pressing devices, there being one pressingdevice for each carrying mechanism, the pressing devices being supportedon the rotor, each pressing device being operable to engage the newpiece carried by the respective carrying mechanism as the rotor advancesthe carrying mechanism past the block and the respective heating deviceis moved into the retracted position, and to press the new piece againstthe block.
 5. The apparatus of claim 4, wherein each pressing devicecomprises a roller arranged to roll along the new piece in thelongitudinal direction.